Low power video security monitoring system

ABSTRACT

If motion occurs in an area viewed by a lens (14) of a video camera (12), a video security monitoring system (10) establishes a communication link with a video monitoring facility and begins transmitting compressed video images of the area. The system (10) is fabricated from CMOS integrated circuits, and operates at a reduced clock frequency while motion is not detected. Reducing the clock frequency lowers the required power thus permitting operation of the system (10) on energy supplied by an ISDN basic access communication channel. If motion occurs, a digital video image compression subsystem (16) begins producing low quality compressed video data for transmission to the monitoring facility. If motion occurs in the central region of the area viewed by the lens (14), then the subsystem (16) produces a single high quality compressed video image. Commands transmitted from the monitoring facility to the video security monitoring system (10) may control its entire operation.

TECHNICAL FIELD

The present invention relates generally to the technical field ofsecurity devices that sense movement, and more particularly, to videosystems for observing an area to detect motion.

BACKGROUND ART

Well known in the art are video security systems that present anobserver located at a video monitoring facility with a succession ofimages of different areas, each area being viewed by a lens of adifferent video camera. However, these video systems are completelypassive in the sense that detecting an intrusion into the area viewed bythe camera's lens remains the responsibility of the observer. That is,the video camera provides the observer with no assistance in detectingan intrusion. Thus, if the observer at the video monitoring facility isdistracted or fails to notice the occurrence of an intrusion, no alarmwill be raised. It is also possible that the occurrence of an intrusionmight be missed because images of other areas are being presented to theobserver at the instant the intrusion occurs. Furthermore, because thevideo signal from each video camera must be transmitted to the videomonitoring facility by a wide bandwidth, coaxial cable, or by some othertype of wide bandwidth, dedicated communication channel such as amicrowave link, it is commercially impractical to distribute this typeof video security system at sites randomly located within an extendedgeographic area, such as throughout a large city.

In addition to well known, passive security systems of the typedescribed above, active, motion sensing video systems have beendeveloped for military battlefield applications. However, theseexperimental military systems were physically very large, e.g. werecarried on a trailer and towed by a jeep, consumed hundreds of watts ofpower, and were very expensive.

Recently, throughout the world, telephone systems have begun providingdigital communication capability in accordance with the IntegratedServices Digital Network ("ISDN") standard established by theInternational Telegraph and Telephone Consultative Committee ("CCITT").Under this CCITT standard, a basic ISDN access consists of twofull-duplex 64 kilobits per second ("kbps") digital data channels,called channel B1 and channel B2, plus another full-duplex 16-kbpsdigital channel, called a D channel. Under the CCITT standard, usingtime division multiplexing, all three of these digital data channels maybe transmitted over a single pair of twisted wires, or over two pairs oftwisted wires. While ISDN basic access was originally intended toprovide voice and slow speed data communication services, over the yearsdevelopments in digital signal processing and compression techniqueshave advanced technology to the extent that compressed video data maynow be transmitted using an ISDN basic access communication channel.These techniques have progressed to such an extent that there now existseveral alternative video data compression techniques such as the CCITTH.261 picture phone standard, the Joint Photographic Experts Group("JPEG") standard, and the Moving Picture Experts Group ("MPEG")standard that permit transmission of video images over an ISDN basicaccess communication channel. Furthermore, the CCITT has established astandard H.221 which permits intermixed transmission over an ISDN basicaccess communication channel of images compressed in accordance withboth the H.261 picture phone standard, and images compressed inaccordance with the JPEG standard.

DISCLOSURE OF INVENTION

An object of the present invention is to provide a video securitymonitoring system that may be economically installed at randomly locatedsites within a large geographic area.

Another object of the present invention is to provide a video securitymonitoring system that assists an observer at a video monitoringfacility in detecting the occurrence of motion in the area viewed by alens of a video camera.

Another object of the present invention is to provide a video securitymonitoring system that detects movement in the area viewed by a lens ofa video camera even thought an observer at a video monitoring facilityis not presently observing an image of the area.

Another object of the present invention is to provide a video securitymonitoring system that may be installed more easily.

Another object of the present invention is to provide a video securitymonitoring system that retains an image of an intrusion for an unlimitedperiod of time thereafter, even following an interruption of electricalpower to the video security monitoring system.

Another object of the present invention is to provide a video securitymonitoring system that may surreptitiously illuminate an area while itis being observed.

Another object of the present invention is to provide a video securitymonitoring system adapted for verifying an individual's authorization toenter the area under observation.

Yet another objection of the present invention is to provide aneconomically practical motion sensing video security monitoring system.

Briefly, a video security monitoring system in accordance with thepresent invention includes a video camera for producing a video signalfrom an image of an area viewed by a lens of the video camera. The videosecurity monitoring system also includes a digital video imagecompression subsystem that receives the video signal from the videocamera. Upon receiving the video signal, the digital video imagecompression subsystem processes the video signal to determine if anymotion is occurring in the area viewed by the camera's lens. If thedigital video image compression subsystem detects motion, it notifies adigital signal transmission interface and control that motion has beendetected.

The digital signal transmission interface and control, which supervisesthe overall operation of the video security monitoring system, uponbeing notified that the digital video image compression subsystem hasdetected motion activates the digital video image compression subsystemto begin converting the video signal into compressed digital video data.After converting the image of the area being viewed by the videocamera's lens into compressed digital video data, the digital videoimage compression subsystem transmits the compressed data to the digitalsignal transmission interface and control. The digital signaltransmission interface and control in turn transmits the compresseddigital video data from the video security monitoring system to a remotevideo monitoring facility.

In the preferred embodiment of the video security monitoring system ofthe present invention, the digital signal transmission interface andcontrol transmits the compressed digital video data to the videomonitoring facility via an ISDN basic access communication channel.Because telephone systems in the industrialized nations generallyprovide ISDN basic access communications, the digital signaltransmission interface and control need establish a connection forcommunicating with the video monitoring facility only if the digitalvideo image compression subsystem detects motion in the area viewed bythe video camera's lens.

Furthermore, because the ISDN basic access communication channelprovides a specified amount of electrical power to a device connectedthereto, operation of a video security monitoring system in accordancewith the preferred embodiment of the present invention may be energizedby electrical power drawn from the ISDN basic access communicationchannel. During intervals in which motion does not occur, the videosecurity monitoring system operates on only a fraction of the electricalpower, i.e., less than one-half watt, provided by the ISDN basic accesscommunication channel. The video security monitoring system operates onsuch a small amount of power because it is fabricated from ComplementaryMetal Oxide Silicon ("CMOS") integrated circuits ("ICs") that operate ata reduced clock frequency when notion is not detected. Energizing thevideo security monitoring system with electrical power drawn from thecommunication channel significantly simplifies installation of a videosecurity monitoring system since only a single electrical connectionmust be established.

A video security monitoring system in accordance with the presentinvention may also include a compressed data memory for temporarilystoring compressed digital video data produced by the digital videoimage compression subsystem. A compressed data memory may beadvantageously included in the video security monitoring system of thepresent invention to temporarily store compressed digital video dataduring an interval between detection of motion by the digital videoimage compression subsystem and establishment of an ISDN basic accesscommunication link between the video security monitoring system and thevideo monitoring facility. If compressed digital video data has beenstored in the compressed data memory, responsive to commands transmittedfrom an observer at the video monitoring facility to the video securitymonitoring system, the system may provide the observer with images ofthe area viewed by the camera's lens beginning at the instant at whichthe digital video image compression subsystem detects motion. Moreover,because the preferred embodiment of the compressed data memory retainscompressed digital video data after an interruption of electrical powerto the video security monitoring system, images stored in the compresseddata memory may be retrieved and viewed long after their occurrence andstorage.

The video security monitoring system of the present invention may alsoinclude a camera control for effecting changes in various settings ofthe video camera responsive to control signals received from the digitalsignal transmission interface and control. For example, the cameracontrol may be adapted for changing the setting of the camera's iris,the focus of the camera's lens, and the lens' zoom if the camera has azoom lens. Furthermore, the camera control may also be adapted fortilting and panning the video camera to change the area viewed by itslens. Analogously, the video security monitoring system may also includea serial control for exchanging signals between the digital signaltransmission interface and control and a monitoring device external tothe video security monitoring system. For example, the serial controlmight exchange signals between the digital signal transmission interfaceand control and a weather station that monitors atmospheric conditions.

A video security monitoring system in accordance with the presentinvention may also include a strobe light for illuminating the areaviewed by the camera's lens. The area viewed by the lens is preferablyilluminated by the strobe light only at the instant the video camera isacquiring an image to be processed by the digital video imagecompression subsystem. This mode of operating the strobe light reducesthe electrical power required by the video security monitoring system.The strobe light is preferably a Light Emitting Diode ("LED") that emitsinfra red illumination. Because an intruder cannot normally perceive thepresence of infra red illumination, if they do not possess an infra reddetector they will be unaware that they are being illuminated by thevideo security monitoring system.

A video security monitoring system in accordance with the presentinvention may also include a stylus having a source of illumination thatmay be directed toward the camera's lens. If an individual appropriatelypositions this stylus while writing an identifying message, for examplewhile writing their name, the video security monitoring system mayverify their authorization to enter the area observed by the videosecurity monitoring system. As with the strobe light, the source ofillumination included in the stylus is preferable an infra red emittingLED.

A video security monitoring system in accordance with the presentinvention may also include a microphone for producing an audio signalfrom sound occurring about the video security monitoring system. If thevideo security monitoring system includes a microphone, it will alsoinclude a digital audio compression-decompression subsystem thatreceives the audio signal from the microphone. Upon receiving the audiosignal, the digital audio compression-decompression subsystem processesthe audio signal to determine if any change in sound has occurred aboutthe video security monitoring system. If the digital audiocompression-decompression subsystem detects a change in sound, thedigital signal transmission interface and control commands it to beginconverting the audio signal into compressed digital audio data. Afterconverting the audio signal into compressed digital audio data, thedigital audio compression-decompression subsystem transmits thecompressed digital audio data to the digital signal transmissioninterface and control. Similar to the transmission of compressed digitalvideo data to the video monitoring facility, the digital signaltransmission interface and control also transmits the compressed digitalaudio data to that facility, and may also store the compressed digitalaudio data in the compressed data memory, if one is included in thevideo security monitoring system.

If the video security monitoring system includes a digital audiocompression-decompression subsystem, that subsystem may also receivecompressed digital audio data from the digital signal transmissioninterface and control. If the video security monitoring system alsoincludes a speaker, the digital audio compression-decompressionsubsystem converts the compressed digital audio data into an audiosignal and transmits that signal to the speaker for producing an audiblesound. Inclusion of a digital audio compression-decompression subsystemand a speaker in the video security monitoring system permits anobserver at the video monitoring facility to communicate audibly withanyone in the vicinity of the system.

These and other features, objects and advantages will be understood orapparent to those of ordinary skill in the art from the followingdetailed description of the preferred embodiment as illustrated in thevarious drawing figures.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram depicting a video security monitoring systemin accordance with the present invention including its video camera, itsdigital video image compression subsystem, its digital signaltransmission interface and control, and its digital audiocompression-decompression subsystem; and

FIG. 2 is a block diagram depicting in greater detail the digital videoimage compression subsystem, the digital signal transmission interfaceand control, and the digital audio compression-decompression subsystemillustrated in FIG. 1.

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 1 is a block diagram depicting a video security monitoring systemin accordance with the present invention identified by the generalreference character 10. The video security monitoring system 10 includesa video camera 12. The video camera 12 may be selected from among thoseprovided by various manufacturers such as a model CCB-C35T sold by SonyCorporation of Japan. The video camera 12 includes a lens 14 that, inthe illustration of FIG. 1, has adjustable iris, focus, and zoom.Depending upon the particular application for the video securitymonitoring system 10, the lens 14 of the video camera 12 may or may notinclude all of these features. The video camera 12 produces video timingsignals and transmits them to a digital video image compressionsubsystem 16 via a video timing signals bus 18. The video timing signalspresent on the video timing signals bus 18 synchronize the operation ofthe digital video image compression subsystem 16 to that of the videocamera 12. In synchronism with the video timing signals, the videocamera 12 produces a video signal of an image of an area viewed by thelens 14 that is transmitted over a video signal bus 22 to the digitalvideo image compression subsystem 16.

Upon receiving the video signal from the video camera 12, the digitalvideo image compression subsystem 16 processes the video signal todetermine if any motion is occurring in the area viewed by the lens 14.The digital video image compression subsystem 16 detects motion bycomparing the video signal for the present image with that of a priorimage seeking differences between the two images. If the digital videoimage compression subsystem 16 detects motion, it notifies a digitalsignal transmission interface and control 24 that motion has occurred bytransmitting data to the interface and control 24 over a system bus 26.

The digital signal transmission interface and control 24 supervises theoverall operation of the digital video image compression subsystem 16,and the video camera 12. If the digital video image compressionsubsystem 16 notifies the digital signal transmission interface andcontrol 24 that it has detected motion, the interface and control 24transmits a command to the subsystem 16 via the system bus 26 commandingit to begin producing compressed digital video data of the area viewedby the lens 14. After converting the image of the area being viewed bythe lens 14 into compressed digital video data, the digital video imagecompression subsystem 16 transmits the compressed data to the digitalsignal transmission interface and control 24 via the system bus 26. Thedigital signal transmission interface and control 24 then transmits thecompressed digital video data from the video security monitoring system10 to a remote video monitoring facility (not illustrated in any of theFIGS.).

In the preferred embodiment of the video security monitoring system 10of the present invention, the digital signal transmission interface andcontrol 24 transmits the compressed digital video data to the videomonitoring facility via an ISDN basic access communication channel 28.While the video security monitoring system 10 of the present inventionpreferably communicates with the video monitoring facility via an ISDNbasic access communication channel 28, the use of various alternativecommunication channels is within the purview of the present invention.Thus, alternative embodiments of the video security monitoring system 10may transmit compressed digital video data to the video monitoringfacility via an ISDN primary access communication channel, via an analogsignal communication channel such as a conventional analog telephoneline, a twisted pair of wires, or a coaxial cable, via an optical fibrecommunication channel, or via a wireless communication channel. If thevideo security monitoring system 10 communicates with the videomonitoring facility via an analog signal communication channel, thedigital signal transmission interface and control 24 of the system 10may include a modem to facilitate transmission of digital data.

The ISDN basic access communication channel 28 provides up to 10milliamperes of direct current at 48 volts, i.e. 0.48 watts ofelectrical power, to the digital signal transmission interface andcontrol 24. The digital signal transmission interface and control 24separates this DC power from the other signals present on the ISDN basicaccess communication channel 28, and transmits the power via an ISDNpower line 34 to a power supply 36 included in the video securitymonitoring system 10. The power supply 36 converts the comparativelyhigh voltage electrical power provided by the ISDN basic accesscommunication channel 28 into voltage(s) suitable for energizing theoperation of the video security monitoring system 10. An electricalpower bus 38 distributes the electrical power produced by the powersupply 36 throughout the video security monitoring system 10 to thevideo camera 12, to the digital video image compression subsystem 16, tothe digital signal transmission interface and control 24, and to otherelectrically powered devices that may be included in the video securitymonitoring system 10.

To permit energizing the operation of the video security monitoringsystem 10 with the power supply 36 during intervals of peak powerconsumption, the power supply 36 includes an electrical energy storagedevice such as a battery (not illustrated in any of the FIGS.). Theelectrical energy storage device included in the power supply 36 storeselectrical energy received from the ISDN basic access communicationchannel 28 during intervals of low power consumption by the videosecurity monitoring system 10, and later supplies that energy to thesystem 10 during intervals of power consumption greater than that whichthe ISDN basic access communication channel 28 supplies to the system10.

The video security monitoring system 10 may also include a compresseddata memory 42 for temporarily storing compressed digital video dataproduced by the digital video image compression subsystem 16. Thecompressed data memory 42 may be advantageously included in the videosecurity monitoring system 10 to temporarily store compressed digitalvideo data during an interval between detection of motion by the digitalvideo image compression subsystem 16 and establishment of the ISDN basicaccess communication link between the video security monitoring system10 and the video monitoring facility. The inclusion of the compresseddata memory 42 in the video security monitoring system 10 assurespreservation of images beginning at the instant the digital video imagecompression subsystem 16 sensed movement.

Because the compressed data memory 42 exchanges data with the digitalsignal transmission interface and control 24 over the system bus 26,compressed digital video data stored in the compressed data memory 42must first be transferred from the digital video image compressionsubsystem 16 to the digital signal transmission interface and control24, after which the digital signal transmission interface and control 24transfers the compressed digital video data to the compressed datamemory 42. The compressed data memory 42 operates as a queue buffer withthe most recent compressed digital video data replacing the oldestcompressed digital video data previously stored in the compressed datamemory 42. If commands received by the video security monitoring system10 from the video monitoring facility request transmission of thecompressed digital video data stored in the compressed data memory 42,then the digital signal transmission interface and control 24 retrievesthe requested compressed digital video data from the compressed datamemory 42 and transmits it to the video monitoring facility.

The compressed data memory 42, which receives its electrical power fromthe electrical power bus 38, is preferably either a low power hard diskdrive having a capacity of at least 20 MBytes, or a corresponding amountof semiconductor FLASH memory. Both of these types of memories retaindata after a power interruption, thus preserving for later recovery thedata most recently stored in the compressed data memory 42. Thus, simplysevering the ISDN basic access communication channel 28 does not destroythe most recent images stored in the compressed data memory 42.

The video security monitoring system 10 may also include a cameracontrol 44 for effecting changes in various settings of the video camera12 responsive to control signals received from the digital signaltransmission interface and control 24 via a camera controls signal bus46. Depending upon the precise configuration of the video camera 12, thecamera control 44, which receives its electrical power from theelectrical power bus 38, may be adapted for changing various differentsettings of the video camera 12. Thus, if the video camera 12 includes afocus adjustment, the camera control 44 may include a focus control 52for adjusting the focus of the video camera 12. Similarly, if the lens14 includes a zoom adjustment, the camera control 44 may include a zoomcontrol 54 for adjusting the zoom of the video camera 12. The cameracontrol 44 may also be adapted to change the area viewed by the lens 14by tilting the video camera 12 up and down, as indicated by thedouble-headed curved arrow 56. Similarly, the camera control 44 may alsobe adapted to change the area viewed by the lens 14 by panning the videocamera 12 from side to side, as indicated by the double-headed circulararrow 58.

A video camera 12 always includes an iris control to permit adapting thecamera 12 to changes in illumination and/or operation of the videosecurity monitoring system 10. For example, even if the video camera 12is located indoors, lights illuminating the area viewed by the lens 13of the video camera 12 may go out due to a power failure. Under such acondition of reduced illumination it is necessary to adjust the iris toincrease the sensitivity of the camera 12. Alternatively, an intrudermight shines something bright into the lens 14 of the video camera 12 inan attempt to "blind" it. Under such a condition of increasedillumination it is necessary to adjust the iris to decrease thesensitivity of the camera 12. Consequently, even in the simplest ofinstallations, the camera control 44 always includes a control 62 foradjusting the iris of the video camera 12. Furthermore, the location ofthe iris need not be limited to the lens 14. Some models of videocameras 12 include an electronic control that function similarly to aniris. Therefore, it is within the purview of the present invention touse the signal for the iris control 62 for electronically adjusting thesensitivity of the video camera 12.

The camera control 44 must be capable of moving each of the cameracontrols identified above, i.e. the focus control 52, the zoom control54, the tilt control 56, the pan control 58, and the iris control 62, intwo directions. That is, the camera control 44 must be capable of firstadvancing the control in a particular direction, and subsequentlyretracting the control in the opposite direction. Consequently, for eachof the controls included in the camera control 44, the control 44 mustreceive two type of control signals from the digital signal transmissioninterface and control 24, one to advance the control, and one to retractthe control.

The video security monitoring system 10 may also include a serialcontrol 66 for exchanging signals, via the camera controls signal bus46, between the digital signal transmission interface and control 24 anda monitoring device (not illustrated in any of the FIGS.) external tothe system 10. The serial control 66 preferably provides bidirectionalinterface 68, such as an RS232 or "S" interface, to permit two-waycommunication between the digital signal transmission interface andcontrol 24 and the external monitoring device. For example, if the videosecurity monitoring system 10 were installed out-of-doors, perhapsmonitoring a construction site, the serial control might exchangesignals between the digital signal transmission interface and control 24and a weather station located at the construction site that sensesatmospheric conditions such as wind speed.

The video security monitoring system 10 may also include a strobe light72 having a LED 74 for illuminating the area viewed by the lens 14.Illumination by the LED 74 of the strobe light 72, which receiveselectrical power from the power supply 36 via the electrical power bus38, may be triggered either by a control signal received from thedigital video image compression subsystem 16 via a first strobe controlsignal line 74, or by a control signal received from the digital signaltransmission interface and control 24 via a second strobe control signalline 76.

The video security monitoring system 10 may also include a stylus 82having a battery powered LED 84 whose infra red radiation may bedirected toward the lens 14. If an individual appropriately holds thestylus 82 to direct light from its LED 84 toward the lens 14 whilewriting an identifying message, for example while writing their name,the video security monitoring system 10 may verify their identity. Suchverification may be made either by visual observation of the image by anobserver at the video monitoring facility, or by a computer programexecuted by a digital computer located at the video monitoring facility,or executed in the digital signal transmission interface and control 24of the video security monitoring system 10.

The video security monitoring system 10 may also include a microphone 92for producing an audio signal from sound occurring about the videosecurity monitoring system 10. The microphone 92 transmits its audiosignal via an audio input line 94 to a digital audiocompression-decompression subsystem 96. Upon receiving the audio signalfrom the microphone 92, the digital audio compression-decompressionsubsystem 96 processes the audio signal to determine if any change insound has occurred about the video security monitoring system 10. If thedigital audio compression-decompression subsystem 96 detects a change insound, it converts audio signal into compressed digital audio data thatit then transmits via the system bus 26 to the digital signaltransmission interface and control 24. Similar to the transmission ofcompressed digital video data to the video monitoring facility, thedigital signal transmission interface and control 24 also transmits thecompressed digital audio data to that facility, and may also store thecompressed digital audio data in a queue buffer in the compressed datamemory 42, if one is included in the video security monitoring system12.

If the video security monitoring system 10 includes the digital audiocompression-decompression subsystem 96, the subsystem may also receivecompressed digital audio data from the digital signal transmissioninterface and control 24. The digital audio compression-decompressionsubsystem 96 converts such compressed digital audio data into an audiosignal and transmits that signal via a audio output line 102 to aspeaker 104.

The Digital Video Image Compression Subsystem 16

Referring now to FIG. 2, depicted there are block diagrams respectivelyof the digital video image compression subsystem 16, of the digitalsignal transmission interface and control 24, and of the digital audiocompression-decompression subsystem 96. As depicted in FIG. 2, thedigital video image compression subsystem 16 receives the video signalfrom the video camera 12 via the video signal bus 22. The Sony CCB-C35Tvideo camera 12 of the preferred embodiment transmits R-Y, B-Y, and Yvideo signals to the digital video image compression subsystem 16.Within the digital video image compression subsystem 16, the R-Y signalfrom the video camera 12 is applied via a R-Y signal line 112 of thevideo signal bus 22 to one input of a 2:1 multiplexer 114. The otherinput of the 2:1 multiplexer 114 receives the B-Y signal from the videocamera 12 via a B-Y signal line 116 of the video signal bus 22.

Responsive to a clock signal supplied to the 2:1 multiplexer 114 fromthe video timing signals bus 18 via a multiplexer control signal line118, the 2:1 multiplexer 114 transmits either the R-Y or the B-Y videosignal to an input of a chroma analog-to-digital converter ("ADC") 122via a chroma signal line 124. The chroma ADC 122 is preferably a TDA8709Video Analog Input Interface IC manufactured by PhilipsComponents-Signetics of Sunnyvale, Calif. The Y signal, that istransmitted to the digital video image compression subsystem 16 from thevideo camera 12, is supplied to an input of a luminance ADC 126 via a Ysignal line 128 of the video signal bus 22. The luminance ADC 126 ispreferably a TDA8708 Video Analog Input Interface IC manufactured byPhilips Components-Signetics of Sunnyvale, Calif. Both the chroma ADC122 and the luminance ADC 126 receive the video timing signals that thevideo camera 12 transmits to the digital video image compressionsubsystem 16 via the video timing signals bus 18. Responsive to thesevideo timing signals, the chroma ADC 122 digitizes either the R-Y or theB-Y signal that it receives from the 2:1 multiplexer 114 while theluminance ADC 126 concurrently digitizes the Y signal. Thus, concurrentoperation of the chroma ADC 122 and the luminance ADC 126 producesuncompressed digital video data.

The uncompressed digital video data produced by the chroma ADC 122 andluminance ADC 126 are transmitted via a video data bus 132 to anIntegrated Information Technology, Inc. ("IIT") Vision Controller ("VC")IC 134. The digital video image compression subsystem 16 also includesan IIT Vision Processor ("VP") IC 136 that exchanges video data with theVC IC 134 via a compressed video data bus 138. Both the VC IC 134 andthe VP IC 136 are manufactured by Integrated Technology, Inc. of SantaClara, Calif. The digital video image compression subsystem 16 alsoincludes a 2 Mbyte or larger frame buffer dynamic random access memory("DRAM") 142. The DRAM 142 is accessed via the compressed video data bus138 by the VC IC 134 and the VP IC 136. The digital video imagecompression. subsystem 16 also includes a 32 Kbyte boot read only memory("ROM") 144 and a 64 Kbyte static random access memory ("SRAM") 146 thatare accessible only to the VC IC 134. Analogously, the VP IC 136accesses its own dedicated 32 Kbyte SRAM 148.

In receiving uncompressed digital video data from the chroma ADC 122 andthe luminance ADC 126, the VC IC 134 operates in synchronism with thevideo timing signals supplied to the digital video image compressionsubsystem 16 by the video camera 12 via the video timing signals bus 18.While the combined VC IC 134 and VP IC 136 are designed for producingcompressed digital video data directly from uncompressed digital videodata, in the video security monitoring system 10 they perform thatfunction only if motion has been detected in the area viewed by the lens14.

If motion has not been detected in the area viewed by the lens 14, tominimize the consumption of electrical power while retaining acapability for detecting motion, the VC IC 134 and the VP IC 136 merelyscan each entire image received from the video camera 12 successivelycomparing a block of pixels from the most recent image with thecorresponding block of pixels from the immediately preceding image. Asthe VC IC 134 and VP IC 136 scan the two images comparing blocks ofpixels, the VC IC 134 cumulates a number representing the average numberof pixels that change between pairs of blocks of pixels processed thusfar for this pair of images. If the average number of pixels that changeper block exceeds a pre-established threshold, then the VC IC 134transmits data to the digital signal transmission interface and control24 via the system bus 26 notifying it that motion has been detected.

If motion is detected, responsive to control data received from thedigital signal transmission interface and control 24, the digital videoimage compression subsystem 16 begins producing video data compressed inaccordance with the CCITT H.261 picture phone standard. In processingvideo data received from the chroma ADC 122 and the luminance ADC 126 toproduce the compressed digital video data, the VC IC 32 preprocessesthat data, supplies the preprocessed video data to the VP IC 136 via thecompressed video data bus 138, and supervises compression of the videodata by the VP IC 136. After the VP IC 136 compresses the video data,the VC IC 134 performs Huffman coding on the compressed data, andtransmits the now Huffman encoded compressed digital video data via thesystem bus 26 to the digital signal transmission interface and control24.

In addition to monitoring consecutive images received from the videocamera 12 for motion and producing compressed digital video data ifmotion has occurred, the VC IC 134 may also transmit a control signal tothe strobe light 72 via the first strobe control signal line 76 thatcauses the strobe light 72 to illuminate the area viewed by the lens 14of the video camera 12.

The Digital Signal Transmission Interface and Control 24

The digital signal transmission interface and control 24 includes amicrocomputer IC 152 that communicates with the VC IC 134 of the digitalvideo image compression subsystem 16 via the system bus 26. The digitalsignal transmission interface and control 24 also includes a 128 KByteROM 154 and a 64 KByte SRAM 156 that may also be accessed by themicrocomputer 152 via the system bus 26. The microcomputer 152 alsocommunicates with an ISDN interface IC 162 via a ISDN data bus 164. TheISDN interface IC 162 receives data from and transmits data to the ISDNbasic access communication channel 28. In addition to supervising theoverall operation of the video security monitoring system 10 describedin greater detail below, the microcomputer 152 also supervises allaspects of the ISDN basic access communication performed by the ISDNinterface IC 162 including call set-up and tear-down.

The microcomputer 152 is preferably a Toshiba TMPZ84C710A and the ISDNinterface IC 162 is preferably a Toshiba TA32032F IC, both of which aremanufactured by Toshiba, Ltd. of Tokyo, Japan. The Toshiba TMPZ84C710Amicrocomputer includes both input-output ports and an interface adaptedfor controlling the operation of an IDE hard disk drive. Consequently,if a hard disk is used for the compressed data memory 42, the memory 42it need only include a single Programmable Array Logic ("PAL") IC forinterfacing to the microcomputer 152.

One of the primary function performed by the microcomputer 152 incontrolling the operation of the video security monitoring system 10 ispower management. The microcomputer 152 employs two strategies formanaging the power consumed by the video security monitoring system 10during intervals in which the digital video image compression subsystem16 does not detect motion in the area viewed by the lens 14. The firststrategy is to transmit control signals via the camera controls signalbus 46 to all portions of the video security monitoring system 10turning off those that are not directly involved in intrusion detection.That is, the digital signal transmission interface and control 24 turnsoff everything but the video camera 12, the digital video imagecompression subsystem 16, the power supply 36, and, if the videosecurity monitoring system 10 includes a microphone 92, the digitalaudio compression-decompression subsystem 96.

The second strategy employed is to transmit control signals via thecamera controls signal bus 46 to the video camera 12, to the digitalvideo image compression subsystem 16, to the digital signal transmissioninterface and control 24, and if the video security monitoring system 10includes a microphone 92, to the digital audio compression-decompressionsubsystem 96 causing them to reduce their clock speed. Because theentire video security monitoring system 10 is preferably fabricatedusing CMOS ICs, reducing the clock speed greatly reduces the amount ofpower required to operate the video security monitoring system 10. Ifthe clock speed is reduced to one-half, the power consumed by the ICsincluded in the video security monitoring system 10 is reduced toapproximately one-fourth of that consumed during full speed operation.If the clock speed is reduced to one-tenth, the power consumed isreduced to approximately one-hundredth of that consumed during fullspeed operation. While the entire video security monitoring system 10consumes approximately fourteen watts of power when operating at fullspeed, the clock speed may be easily reduced to such an extent that thepower consumed is significantly less than that provided by a ISDN basicaccess communication channel while maintaining full capability to detectmotion occurring in the area viewed by the lens 14.

A consequence of reducing the clock speed of the video camera 12 whenthere is no motion in the area viewed by the lens 14 is that the videocamera 12 becomes more sensitive. Because of the increased sensitivityof the video camera 12, either the camera 12 must automaticallycompensate for the increased sensitivity by adjusting its iris, or themicrocomputer 152 must adjust the iris to reduce the sensitivity of thevideo camera 12.

If the digital video image compression subsystem operating at reducedspeed detects movement in the area viewed by the lens 14, themicrocomputer 152 then signals the various circuits in the videosecurity monitoring system 10 to begin operating at full speed andcapacity. Consequently, when the clock speed increases the digitalsignal transmission interface and control 24 commands the VC IC 134 andVP IC 136 to begin producing digital video data compressed in accordancewith the CCITT H.261 standard. If motion is detected, the microcomputer152 also immediately causes the ISDN interface IC 162 to place atelephone call to the video monitoring facility. After the videosecurity monitoring system 10 is in communication with the videomonitoring facility it will begin transmitting compressed digital videodata there. At the same time, commands may be sent from the videomonitoring facility to the video security monitoring system 10 forcontrolling its operation.

In the preferred embodiment of the video security monitoring system 10,if movement enters a central region of the image, the system 10temporarily interrupts compressing the video data in accordance with theH.261 standard to compress a single image using the much higher qualityJPEG image compression standard. By communicating data between the videosecurity monitoring system 10 and the video monitoring facility inaccordance with the CCITT H.221 standard, this higher quality JPEG imagemay be intermixed with the lower quality H.261 images for transmissionthe video monitoring facility over the ISDN basic access communicationchannel 28.

The video security monitoring system 10 incorporates certain features tofacilitate its installation and operation. For example, the videosecurity monitoring system 10 always responds to a telephone call. Thus,the video monitoring facility may always call the video securitymonitoring system 10 to confirm its proper operation. Furthermore, ifafter responding to a telephone call the video security monitoringsystem 10 receives a specified command and if no data specifying atelephone number is presently stored at a specified location in the SRAM156, the system 10 then accepts and stores of a telephone numbertransmitted from the video monitoring facility. The video securitymonitoring system 10 will then call that telephone number if itsubsequently detects motion as described above. The video securitymonitoring system 10 may also provide a feature of immediately callingback to the telephone number immediately after its storage in the SRAM156. This call-back feature provides a means for immediately confirmingthat the video security monitoring system 10 is operating correctly andthat the correct telephone number has been stored in the SRAM 156.

The Digital Audio Compression-Decompression Subsystem 96

As illustrated in FIG. 2, if the digital audio compression-decompressionsubsystem 96 is included in the video security monitoring system 10, thesubsystem 96 includes a TMS320C25 digital signal processor ("DSP") IC172. The DSP IC 172 processor is more completely described in the "TexasInstrument DSP Hand Book" and is manufactured by Texas InstrumentsIncorporated of Dallas, Tex. In addition to the DSP IC 172, the digitalaudio compression-decompression subsystem 96 includes a 64 KByteSRAM.174 that exchanges data with the DSP IC 172 over a compressed audiodata bus 176. The digital audio compression-decompression subsystem 96also includes a CS4215 Stereo Audio Codec IC 178 manufactured by CrystalSemiconductor Corporation of Austin, Tex. The audio codec 178 includesan ADC 182 and a digital-to-analog converter ("DAC") 184.

If the video security monitoring system 10 includes the microphone 92,the ADC 182 receives the audio signal from the microphone 92 via theaudio input line 94. The ADC 182 then digitizes this audio signal togenerate digitized audio data that it transmits to the DSP IC 172 via adigitized audio input data bus 186. Similar to the VC IC 134 and the VPIC 136, the DSP IC 172 monitors the digitized audio data to detect ifthere is a change in the sound about the video security monitoringsystem 10. If a change in sound occurs, the DSP IC 172 transmits dataover the system bus 26 to the digital signal transmission interface andcontrol 24 notifying it of the event. The microcomputer 152 responds tothis notification by transmitting control signals to the digital audiocompression-decompression subsystem 96 which increases the clock speedof the DSP IC 172 and cause it to begin converting the digitized audiodata into compressed digital audio data and transmitting the compresseddigital audio data to the digital signal transmission interface andcontrol 24 via the system bus 26. The DSP IC 172 compresses thedigitized audio data in accordance with one of the audio compressionstandards, such as the CCITT standard G.711 or G.722, that adapt audiodata for transmission over an ISDN communication channel. Concurrentwith initiating production of compressed digital audio data by thedigital audio compression-decompression subsystem 96, the microcomputer152 also places a telephone call to the video monitoring facility, andbegins storing the compressed digital audio data in a queue buffer onthe compressed data memory 42 if one is included in the video securitymonitoring system 10.

If the video security monitoring system 10 includes the speaker 104,then the DSP IC 172 may receive compressed digital audio data from thevideo monitoring facility via the ISDN basic access communicationchannel 28, the ISDN interface IC 162, the microcomputer 152, and thesystem bus 26. Upon receiving such compressed digital audio data, theDSP IC 172 decompresses it and transmits it via a digitized audio outputdata bus 188 to the DAC 184. Upon receiving the digitized audio data,the DAC 184 converts it to an audio signal that it transmits via theaudio output line 102 to the speaker 104.

INDUSTRIAL APPLICABILITY

While operation of the video security monitoring system 10 is preferablyenergized by electrical energy received through the ISDN basic accesscommunication channel 28, the system 10 may also receive its electricalpower through any of the communication channels identified above exceptfor the optical fibre communication channel and the wirelesscommunication channel. Since operation of the video security monitoringsystem 10 with either of these two latter communication channelsrequires another source of electrical power to energize the operation ofthe system 10, it is within the purview of the present invention toenergize the operation of the system with electrical power suppliedeither from a communication channel or from some other source.

The VC IC 134 and the VP IC 136 of the preferred embodiment of the videosecurity monitoring system 10 detect motion in the area viewed by thelens 14 by successively comparing 8-by-8 blocks of pixels taken from twoconsecutive images. However, it is within the purview of the presentinvention to compare blocks of pixels containing fewer or more than 64pixels.

The preferred embodiment of the video security monitoring system 10employs standard protocols for compressing digital video and digitalaudio data. Thus, display systems capable of presenting an image and/orsound respectively either from digital video data or digital audio datacompressed in accordance with such standards may be employed in thevideo monitoring facility.

While the preceding description of the video security monitoring system10 has emphasized its capability for detecting either motion or a changein sound and alerting the video monitoring facility to such an event, atany time an operator at the video monitoring facility may initiatecommunication with the video security monitoring system 10 to send itcommands for controlling its operation. Such operator commands mayinclude any operation of which the video security monitoring system 10is capable, including directing the video security monitoring system 10to transmit either compressed digital video data of an image orcompressed digital audio data of sound back to the video monitoringfacility.

Although the present invention has been described in terms of thepresently preferred embodiment, it is to be understood that suchdisclosure is purely illustrative and is not to be interpreted aslimiting. Consequently, without departing from the spirit and scope ofthe invention, various alterations, modifications, and/or alternativeapplications of the invention will, no doubt, be suggested to thoseskilled in the art after having read the preceding disclosure.Accordingly, it is intended that the following claims be interpreted asencompassing all alterations, modifications, or alternative applicationsas fall within the true spirit and scope of the invention.

What is claimed is:
 1. A video security monitoring system comprising:avideo camera for producing a video signal from an image of an areaviewed by a lens of said video camera, said video camera including aniris control; a digital video image compression subsystem for receivingthe video signal from said video camera, for digitally processing thevideo signal to determine if any motion is occurring in the area viewedby the lens of said video camera, for converting the video signal intocompressed digital video data that provides an image of the area viewedby the lens of said video camera, and for transmitting the compresseddigital video data; a digital signal transmission interface and controlfor controlling operation of said video camera and said digital videoimage compression subsystem, for receiving the compressed digital videodata from said digital video image compression subsystem, and fortransmitting the compressed digital video data from said video securitymonitoring system to a remote video monitoring facility via acommunication channel if said digital video image compression subsystemdetermines that motion has occurred in the area viewed by the lens ofsaid video camera, said digital signal transmission interface andcontrol also managing power consumption by said video securitymonitoring system by causing said video camera and said digital signalimage compression subsystem to operate at a slower clock speed whenmotion is not present in the area viewed by the lens of said videocamera and to operate at a faster clock speed upon detecting motion inthe area viewed by the lens of said video camera; and a cameracontroller for effecting changes in settings of the iris control of saidvideo camera to compensate for changes in video camera sensitivityresulting from operation of said video camera at different clock speedsin effecting power management of said video security monitoring system.2. The video security monitoring system of claim 1 wherein said digitalsignal transmission interface and control transmits the compresseddigital video data from said video security monitoring system via anISDN basic access communication channel.
 3. The video securitymonitoring system of claim 1 wherein said digital signal transmissioninterface and control transmits the compressed digital video data fromsaid video security monitoring system via an ISDN primary accesscommunication channel.
 4. The video security monitoring system of claim1 wherein said digital signal transmission interface and controltransmits the compressed digital video data from said video securitymonitoring system via an analog signal communication channel.
 5. Thevideo security monitoring system of claim 4 wherein said digital signaltransmission interface and control further includes a modem fortransmitting the compressed digital video data from said video securitymonitoring system via the analog signal communication channel.
 6. Thevideo security monitoring system of claim 1 wherein said digital signaltransmission interface and control receives electrical power forenergizing operation of said video security monitoring system from thecommunication channel.
 7. The video security monitoring system of claim6 further comprising a power supply for adapting electrical energyreceived from the communication channel for energizing the operation ofelectronic circuits included in said video camera, said digital videoimage compression subsystem, said digital signal transmission interfaceand control, and said camera controller.
 8. The video securitymonitoring system of claim 7 wherein said power supply also storeselectrical energy for energizing operation of said video securitymonitoring system.
 9. The video security monitoring system of claim 8wherein said power supply stores electrical energy in a battery.
 10. Thevideo security monitoring system of claim 1 wherein said digital signaltransmission interface and control transmits the compressed digitalvideo data from said video security monitoring system via an opticalfibre communication channel.
 11. The video security monitoring system ofclaim 1 wherein said digital signal transmission interface and controlbroadcasts the compressed digital video data from said video securitymonitoring system via a wireless communication channel.
 12. The videosecurity monitoring system of claim 1 wherein said video camera furtherincludes a focus control, and said camera controller effects changes insettings of the focus control responsive to control signals receivedfrom said digital signal transmission interface and control.
 13. Thevideo security monitoring system of claim 1 wherein said video camerafurther includes a zoom lens, and said camera controller effects changesin settings of the zoom lens responsive to control signals received fromsaid digital signal transmission interface and control.
 14. The videosecurity monitoring system of claim 1 wherein said camera controllertilts said video camera responsive to control signals received from saiddigital signal transmission interface and control.
 15. The videosecurity monitoring system of claim 1 wherein said camera controllerpans said video camera responsive to control signals received from saiddigital signal transmission interface and control.
 16. The videosecurity monitoring system of claim 1 further comprising a serialcontrol for exchanging digital signals between said digital signaltransmission interface and control and a monitoring device external tosaid video security monitoring system.
 17. The video security monitoringsystem of claim 16 wherein said monitoring device transmits signals tosaid video security monitoring system responsive to atmosphericconditions.
 18. The video security monitoring system of claim 1 furthercomprising a compressed data memory for temporarily storing compresseddigital video data transmitted from said digital video image compressionsubsystem.
 19. The video security monitoring system of claim 18 whereinsaid compressed data memory retains compressed digital video data storedtherein even after interruption of all electrical power that energizesoperation of said video security monitoring system.
 20. The videosecurity monitoring system of claim 19 wherein said compressed datamemory stores compressed digital data on a magnetic recording device.21. The video security monitoring system of claim 19 wherein saidcompressed data memory stores compressed digital data in a FLASHsemiconductor memory.
 22. The video security monitoring system of claim1 further comprising a strobe light for momentarily illuminating thearea viewed by the lens of said video camera.
 23. The video securitymonitoring system of claim 22 wherein said strobe light emits a pulse oflight respensive to a signal received from said digital signaltransmission interface and control.
 24. The video security monitoringsystem of claim 22 wherein said strobe light emits a pulse of lightresponsive to a signal received from said digital video imagecompression subsystem.
 25. The video security monitoring system of claim1 further comprising a light emitting stylus that emits light directedtoward the lens of said video camera for presenting an image indicatingmotion of said stylus to said video camera.
 26. The video securitymonitoring system of claim 1 further comprising:a microphone forproducing an audio signal from sound occurring about said video securitymonitoring system; and a digital audio compression subsystem forreceiving the audio signal from said microphone, for digitallyprocessing the audio signal to determine if any change in sound hasoccurred about said video security monitoring system, for converting theaudio signal into compressed digital audio data of sound occurring aboutsaid video security monitoring system, and for transmitting thecompressed digital audio data to said digital signal transmissioninterface and control.
 27. The video security monitoring system of claim1 further comprising:a digital audio decompression subsystem forreceiving compressed digital audio data from said digital signaltransmission interface and control, for converting the compresseddigital audio data into an audio signal, and for transmitting the audiosignal; and a speaker for receiving the audio signal from said digitalaudio decompression subsystem and producing an audible sound therefrom.28. A method for operating a video security monitoring system, the videosecurity monitoring system including a video camera and a digital videoimage compression subsystem that are fabricated using digital circuitswhich operate in response to a clock signal, said method comprising thesteps of:providing a slow clock signal to the digital circuits includedin the video security monitoring system whereby the video securitymonitoring system requires a low amount of electrical power; producing avideo signal from an image of an area viewed by a lens of the videocamera and transmitting the video signal to the digital video imagecompression subsystem; digitally processing the video signal in thedigital video image compression subsystem to determine if any motion isoccurring in the area viewed by the lens of the video camera; if motionis detected in the area viewed by the lens of the video camera,providing the digital circuits included in the video security monitoringsystem with a faster clock signal thereby changing video camerasensitivity and increasing the amount of electrical power required bythe video security monitoring system, and altering an iris of the videocamera to compensate for a change in video camera sensitivity andcommencing conversion by the digital video image compression subsystemof successive images of the video signal received from the video camerainto compressed digital video data to produce compressed digital videodata for a sequence of images of the area viewed by the lens of thevideo camera; and transmitting the compressed digital video data fromthe video security monitoring system to a remote video monitoringfacility via a communication channel.
 29. The method of claim 28 furthercomprising the steps of:compressing the video signal to produce a lowerquality image while the digital video image compression subsystemdetects no motion within a central region of the image; and compressingthe video signal to produce a higher quality image if the digital videoimage compression subsystem detects motion in the central region of theimage.